US1718193A

US1718193A - Apparatus for grinding tools

Info

Publication number: US1718193A
Application number: US504020A
Authority: US
Inventors: Vlieg Gerard A De
Original assignee: Individual
Current assignee: Individual
Priority date: 1921-09-29
Filing date: 1921-09-29
Publication date: 1929-06-18
Anticipated expiration: 1946-06-18

Description

" 1 G. A: DE VLIEG v APPARATUS FOR qnnmme TOOLS "J1me 18, 1929.

9 Sheets-Sheet 1 Filed Sept. 29, 1921 June 18, 1929. G. A. DE VLIEG I APPARATUS FOR GRINDING TOOLS Filed Sept 29, 1921 9 Sheets-Sheet 2 June 18, 1929. 5 VLIEG 1,718,193

' I APPARATUS FOR GRINDING TOOLS Filed Sept. 29, 1921 9 Sheets-Sheet 3 June 18, 1929. I 5. A. DE VLIEG APPARATUS FOR GRINDING TOOLS Sept. 29, 1921 9 Shet-Sheet 5 1 4 imrl 6% 17 6 69 June 18, 1929.

G. A. DE VLIEG APPARATUS FOR GRINDING TOOLS 9 Sheets-Sheet 6 Filed Sept; 29', 1921 W Cz a. $6 ma figj-4 E Q June 18, 1929. e. A. DE VLIEG APPARATUS FOR GRINDING TOOLS Filed Sept. 29, 1921 9 sheets-Shea 8 June18, 1929. QADE VLIEG 1,718,193

Patented June 18, 1929.

UNITED STATES GERARD A. nn vmn'e; or JANESVILLE, WISCONSIN.

APPARATUS FOR GRINDING moons.

Application filed September 29, 1921. Serial No. 504,020.

My invention relates to apparatus for grinding tools, and has for its object the provision of a new and improved grinding machine whereby the ground tools need not have I their ground edges further dressed after they are ground.

The invention is of particularly service when employed in the grinding of reamer blades as by means of it such blades are provided with cutting edges that lie in cylindrical areas. The invention also provides means whereby the ends of the blades may have the portions of the cutting edges therein ground upon lines that taper from the aforesaid cylindrical area.

In the preferred embodiment of the invention the grinding instrument is an emerywheel and the blades to be' ground are upona' blade holder which may be a permanent part W of the machine or which may be the identical blade holder which supports the blades in reaming operations.

The grinding wheel is desirably givena substantially fixed plane of rotation suitably.

inclined with respect to the blade holder for purposes which will later be set forth and the blade holder itself is also turned'but is moved longitudinally of its axis in order -thatthe various portions of the blade being ground may be properly presented tothe grinding wheel to impart the proper shape to the'cutting edge upon the blade that. results 7 from the grinding operation.

I will explaln my invention more '35 reference to the accompanying drawings showing the preferred embodiment thereof as employed in a machine for grinding one form of reamer blade. In the drawings Fig. i

1 is a plan view of such a machine; Fig. 2 is 'a sectional view on line 2--2 of Fig. 1; Fig. 3 is a sectional View on line 33 of Fig. 2;

- Fig. 4 is a sectionalview on line M4 of Fig. 2; Fig. '5 is a sectional view on line 5'5 of Fig. 2;

Fig. 6 is an end view at the left hand end of 15. Fig. 2.;Fig 7 is a sectional view on line 77 of- Fig. 1; Fig. 8 is a sectional view on line 88 of Fig. '7; Fig. 9 is a sectional view 0 J'ne 9--9 of Fig. 7 Fig. 10 is a diagrammgsljc view illustrating the relative dispositio of the work holder and grinding mechanism, the view being taken in the direction of arrow 10, Fig. 1; Fig. 11 is a sectional view on line 11--11 of Fig. 2; Fig. 12 is a motion chart; Fig. 13 is a view taken in a vertical plane in the direction of arrow 13, Fig. 2; Fig. 14:is'a.

sectional View on line 1414 of Fig. 13; Fig.

work holder alongits axis, parts of the cam mechanism being in the position which cause the location of the blade or work holder which is illustrated in Figs. 13 and 14:; Fig. 20 shows thecam mechanism of Fig. 19 with its parts positions indicated by full lines being that which accompanies the adjustment ofthe work holder shown in full lines in Figs. 15

land 16 and the positions shown by dot and dash lines being that which accompanies the adjustment of the work holder shown by dot and dash lines in said Figs. 15 and 16; Fig. 21 shows the cam mechanism with its parts in the relative positions resulting in the adjustment of the work holder shown in Figs. 17 and.18-; Figs.-22,"23'afid 24 are otheryiewsShowing the relations of the work holder arid grinder that respectively accompany the relative positions of the cam parts shown in Figs. 19, 20 and 21; andFigsJ25, 26 and 27 respectively indicate the work holder in full end elevation but turned to different positions in the course of the sharpening of a single blade, the grinder being illustrated in each of these figures also.

Like parts are i dicated by smiilar-characters of reference throughout the difierent figures.

to be limitedtb the use to which the sharpened I blades are to be put, nor is the invention to be limited to the sharpening of reamer blades.

The machine illustrated is one which is in twoother relative posltions, the relative The blade or work holder has slots 2 out A therein, these slots lying in straight planes which are oblique to the axis of rotation of the work holder. This work holder may form a permanent part of the blade grinding machine or may be the identical work holder upon which the blades are mounted when they are put to service. So far as the invention is concerned it will be realized that there may be but one of the slots 2 in the work holder; a plurality being employed for economy in operation as that a number of blades may be subject to the grinding operation in each cycle of movements of the work holder. For the sake of clearness these slots are not shown in those figures which are more or less diagrammatic as extending clear through the work holder from end to end as such an illustration of the slots would serve greatly to confuse the diagrammatic illustrations.

There are-six such slots each containing a reamer blade 3. The machine illustrated is constructed and adjusted so to grind the reamer blades as to impart the desired cutting faces thereto and also to impart suitable shapes to the cutting edges of the blades, the cutting faces and edges of all the blades upon a given work holder being similar. The cutting edge of each blade illustrated has, after the grinding operation, an intermediate portion 4 (Fig. 25) that lies in a cylindrical area cenformingto theiarea of the cylindrical surface which the blades are'to' form upon the interior of a cylinder. Each such cutting edge has one end portion 5 which is the first to enter into engagement with a cylinder that is to be reamed, this portion being termed the lead and tapering from the cylindrieals area with which the portion 4 is coincident. The other end portion 6 of each cutting edge also tapers from said cylindrical area and is commonly termed the backofi'. The cutting edge of each blade is thus a line that lies partially in a cylindrical area at its intermediate portion and in continuing end portions in areas that taper from such cylindrical area, but it is to be understood that the invention is not to be to the varying directions of the cutting edges nor to the grinding of the cutting edges altogether by the machine. Each blade is bevelled from its cutting edge toward the axis of the blade holder so as to produce the necessary clearance back of the cutting edge between the blade and the work upon which it operates, this bevelling being indicated at 7 The machine of my invention employs a blade grinding tool which is preferably in the form of emery wheel 8. This emery wheel and the blade holder are so related and relatively operated that the emery wheel has a line of grinding contact with each blade that is identical with the shape of the cutting edge of the blade which the grinding wheel is to form. To this end the shaft 9 upon which the blade holder is fixed is caused to turn in order'that the blade holder may be limited;

peripheral edge of the grinding wheel,'this edge being represented by a single line in Fig. 10, has grinding contact with the blades, the rearv face of the grinding wheel being cupped so .that the grinding edge of the wheel may be easily sharpened when'desired. The shaft of the grinding wheel is so mounted that the grinding edge is in grinding contact with each blade in a cord of the circle of rotation of the ground blade edge to produce the bevel 7 The plane of rotation of the grinding wheel that is defined for it for producing the bevel upon each blade is at an angle to the axis of the blade holder. In Fig. 10 a vertical plane is illustrated by dot and dash lines at 11 which is-pa-rallel with the horizontal axis of the Work holder, thegrinding wheel being inclined from the plane 11 to its true grinding plane at the angle a Z) c to impart the desired bevelling of the blades. is concerned, the plane of rotation of the grinding wheel need only'be inclined to the horizontal while remaining parallel with the axis of the blade holder but it is slightly inclined with respect to such axis in order that the grinding wheel may grind each blade So far as the mere bevelling without having any improper grindiiigcon themutting edge of the blade is to conform passing through this fixed point (i b suitable longitudinal movement of the bla e holder along the blade holder axis The two angles a Z) 0 and d e f are such that the plane of the grinding wheel slopes downwardly and away from the blade holder to an extent that will .cause the grinding edge of the grinding wheel to sweep over each blade being ground in lines that are substantially at right angles to the cutting edge of such blade throughout the length of the blade so that such cutting edge will be uniformly shar 'ened throughout its"'length which would not e the case if the grinding lines across its bevel face were not paralleland at right angles. The plane of rotation of the grinding wheel is preferably fixed but the blade holder or rather the shaft 90f the blade holder is" so mounted that it may be shifted longitudinally of its axis and shiftingmeehanisni is employed, hereline of grinding contact of the grinding wheel'upon each blade as the blade holder is moved conforms exactly to the shape of the cutting ed" e that is to be produced while at the same time the-proper bevel is being imparted'to the blade owing to the shifting of the blade from the plane 11 through the angle a b 0. Analyzing the diagram of Fig. 10 somewhat further, the shifting of the plane of rotation of the grinding edge of the grinding wheel from the vertical plane 11 that the axis 12. z of the grinding wheel is inclined from the horizontal plane containing the axis 70 Zbf the blade holder, this inclination being measured by the angle h i m (the point-i lying in the plane 11) and is at an angle to the Vertical plane containing such work holder axis, this angle being the angle me n. The point 91. would lie in theaxis. h z' of the grinding wheel if the plane of-rotation of this rinding w'heel were vertical and parallel with the axis of the blade holder but since the planeof the grinding wheel is caused to be angular to the vertical plane containing the axis of the blade holder and slopes downwardly and away from such plane, the

. point 72; (which marks the relocation of the point is swung upon the center i the veri tieal distance km and is also swun upon the "point i the oblique distance it a w ereby the plane of grinding contact of the-wheel is disposed as described for the; purposes set forth.

- The straight line including the point i and the point of contact of the grinding wheel-8 with the blade being sharpened is preferably at 45 to the horizontal with the particu-' lar blade inclination, this line lying in theplane 11 and being coincident with a diameter of the grinding plane of the cutting wheel 8 if this grinding plane were in the plane 11.

This lineand diameter shift with the shift-' ing ofthe grinding plane of the wheel 8 but is still substantially at an angle of 45 -to the horizontal but in a plane which is angular 'to the vertical plane containing the blade holder axisjc Z and slopes from the'horizontalplane containing such blade holder axis. The planell is tangential to the circle of" rotation of the cutting edge of the blade; When this plane is shifted through the anglea I) 0 (which is the bevelling angle) the plane of grinding contact of the Wheel is on a cord of the circle of rotation of the cutting edge of the blade so as to bevel the'blade. The diameter of the grinding wheel that in; eludes the point-(land the centerof the grind- .ing circle" of the grindingwheel continue to lie in the plane do p 9 that is adjusted to be at 45 to, the horizontal, if the blades are mounted'at 45 to the horizontal, the angulari-ties of the planed o .p q and-of. the blades "holder is turned and been ground the blade holder is very rapidly being coincident. As the grinding wheelis tilted the center of the grinding circle is maintained in the 45 plane or other plane that corresponds in angularity to the angu- I Wl1enevcr the cylinder is turned within r I -its holder the shaftlO is elevated or dethrough the angles a?) a and d e f is such pressed according to the direction'in which the cylinder-is turned. Themechanism for holding the cylindyr in its adjustment will later be set forth. The axis of the cylinder 16 substantially includes the substantially fixed grinding point d. If each blade v happens to be at an angle to thehorizontal less than that shown the cylinder 16 is turned to elevate the "grinding Wheel shaft 10. If

each blade happens to be at an angle to the horizontal more than that illustrated the 8 0 d, the planes of these two. angles likewise I being parallel.

\ In the motion chart, Fig. 12 the time to complete one-sixth of a revolution of the blade holder is represented by the space between the lines If and t, and the space between these two lines being evenly divided by the lines t to denote uniform division of time as the rotation of the blade holder is preferably at a constant speed.' The blade holder is. moved along its axis to pass a blade along the grinding poi 1t d as the blade en each blade has returned and again is moved along its axis to pass the next succeeding bladealong the grinding point d as .the blade holder is turned. The rate of lineal travel of the blade holder during the-grinding operation varies as is-indicated by the upright lines in the motion chart. This rate increases in the initial part of the grindin operation until the upright line a isreache ,gwhereby the backofi' 6* is groundir'r the ,bladelfedge." The rate of lineal travel then continues constant until the uprightline v is reached whereby the constant portion 4 of the cutting edge is produced, this constant portion lying within a cylindrical area. After this portion of the blade has been ground the rate of lineal travel of the blade holder increases until the line w is reached whereby the lead 5 of the cutting edge is produced. Just after the lead portion 5 has been produced the blade commenced and the grinding being finished shortly before such line is concluded. The

heavy line y shows the'resultant of the turn-- ing movement and the very rapid reverse lineal movement of the blade holder preparatory to the grinding operation upon an ensuing blade. Adjacent blades upon the blade holder are in spaced apart zones, the line 3 being generated during the rapid re turn movement of the blade holder while the space'between the adjacent zones is traversing the fixed point (Z.

Any suitable means may be employed for holding the cylinder 16 in its adjustment. In the preferred embodiment a bolt 18 is employed that freely passes through a sleeve 19 into threaded connection with an elongated nut 20, the portions 19and 20 being located within a space 21 formed in an enlargement of the holder 17 and into which space a peripheral portion of the cylinder 16 projects so as to be engageable by the sleeve 19 and the nut 20 on the opposite sides of a diametrica-l line. By turning the bolt 18 in one direction or the other the nut and sleeve may be spread apart to free the cylinder 16 to permit its adjustment or may be brought together to hold the cylinder 16 in its adj ustment according to the direction in which the bolt is turned. For convenience the cylinder 16 may be provided with a handle 22 wheel being respectively the lines '5 a and d 0.

to enable the cylinder to be turned when the bolt 18 is loosened.

The shaft 10 has a pulley 23 fixed thereon over which a driving belt 24 passes in order to drive the shaft, this belt passing through a gap 25 in the cylinder 16.

The grinding wheel 8 is bodily adjustable toward and from the blade holder 1 along horizontal lines that respectively include the center i and the point d, the lines followed in this bodily adjustment of the grinding This adjustment permits the grinding wheel to operate upon blades held in holders of different diameters. Any new location of the point of grinding contact with the blades is in a horizontal line that intersects the axis of the blade'holder whereby the timing of the cams, that are later to be described, that control the various operations,'is not disturbed.

The mechanism for eflecting the adjustment of the grinding wheel toward and from the blade holder is preferably inclusive of a stationary threaded shaft 26 mounted upon the frame of the machine. The nut 27 is in mesh with the shaft 26. This nut is formed with worm threads upon its exterior surface that constitute it a worm wheel. These work threads are engaged by the threads upon an adjusting shaft 28 which is mounted to turn in a bearing 29 carried by the cylinder holder 17. A wheel 30 is fixed upon the upper end of the shaft 28. By turning this wheel the worm wheel 27 is turned and as the shaft 26 is fixed, this worm wheel will move along such shaft as said wheel is turned. The wheel is snugly received in the space between the lugs 31, that depend from the holder 17 so that said holder, together with the cylinder 16 therein, the shaft 10 mounted in the cylinder,

and the grinding wheel are together moved" toward or from the blade holder whenever the wheel 27 is turned. The base portion of the holder has a dovetailed recess which receives a'dovetailed guide 32 that is stationary upon the frame of the machine whereby the holder may readily be moved along the guide that keeps the holder from-turning and permits it to move along the guide The shaft 9 of the blade holder is itself mounted between and upon the conical bearings 33 formed upon the inner ends of the shafts 34 that are mounted in the tail stocks 35 which are clamped on the tables 36 that are themselves clamped upon the opposite ends of the single table 37 by means of bolts 38, the tables 36 having sliding engagement with the table 37 so that the tables 36 may be adjusted along the table 37 to permit of the insertion of substitute-d shafts 9 whether these shafts are of the same or different lengths. The heads of said bolts are receivable within a longitudinal grooveway 38' formed in the table 37 so that the bolts, be-

ing loosened, may move with the tables 36 as j they are adjusted along the table 37. To permit extended adjustingmovement of the tables 36 along the table 37 the tables 36 may have a number of bolt holes 38 arranged along the tables in any of which said bolts may be placed The table 37 that supportsboth tables 36 itself has dovetailed mortise and tenon connection 39 with thebase of the machine to permit the table 37 to be moved along the axis of the shaft 9 in one direction as the blade is being ground and in a reverse direction after the grinding of each blade preparatory to the grinding of the next blade. The arrangement is such that a shaft with a plurality of blade holders may be located be-' tween the tail stocks, these tail stocks being adjusted along the table 37 in order properly which not only drives the belt 24 that turns the grinding wheel shaft 10, but also drives is moved along the axis of this roller the rollthe belt 41 that in turndrives the shaft 42 which serves, through the intermediation of suitable transmission mechanism, to reciprocate the bed 37. The shaft 42 is a worm shaft in mesh with the worm wheel'43 that is in fixed relation with a spur gear. cone 44 any of whose spur gears is engageable with a spur gear 45 of proper size fixed upon the shaft 46 mounted in bearings 47 constituting. fixed ex.- tensions of a sleeve 48 which itself surrounds a sleeve 49 and is slidable along the'same but is normally held in fixed relation therewith p by means of the inwardly spring pressed plunger 50 carried by the sleeve 48 and engageable with any of the holes 51 that are distributed along the sleeve 49 and are in the planes of the various spur gears 44. This arrangement permits of the employment of gear wheels 45 of different sizes for engage:

ment with gears 44 of corresponding sizes to regulate the relative rates of revolution of the cone 44 and the pinion (45) upon the shaft 46 so that the gear 52 in mesh with such pinp ion 45 may have its rate of rotation likewise adjusted in relation to the rate of rotation of said gear cone 44. .The'gear 52 is elongated so that it maybe engaged by the gear 45 wvherever this gear is disposed to have meshing engagement. with the gear 44 corresponding to it. A worm gear 53 is eo-axial with and fixed with respect to the elongated gear 52 and is in mesh with anotherworm gear 54 that is fixed'upon the shaft 55 which carries cams 56, 57 and 58, any one of thesecams alone being employed in effecting the longitudinal movement of the table 37 during the grinding operation. The cams are of different shape to effect difierent rates of movement of the table 37, that cam being selected for use acv59 and 60 is primarily controlled by the particular spur gear 44 which is employed ,to

. drive the gear 52 that drives the shaft 55.

The selected cam 56, 57 or 58 performs its functions through the intermediation of the be employed.

cam roller 61 which is adjustable into the plane of rotation of the selected cam pref-' erably by being mounted upon a shaft 62 which is adjustable longitudinally of its axis in a forkedbearing63. The mechanism for adjusting the cam roller 61 and its shaft 62 along the common axis of these two elements preferably includes a notched block 64 which the axisof the shaft 62. This block 64 is formed with a notch 65 that receives the periphery of the roller 61 so that as the block 64 handle carries an inwardly spring pressedlunger that is engageable within either of the

holes

71, 72, 73 respectively corresponding is mounted to' slide in the bearing 63 along to the cams 56, '57 and 58. .When the handle is turned to place 'the plunger 7 Din the selected hole the cam rolleris placed in the plane of rotation of the selected 'eam whereby the final adjustment of the speed of travel of the table 37 in the grinding operation is effected.

The restoring

cams

59 and 60 operate upon the cam rollers .74 and 75. These cam rollers are mounted to turn upon theU-shaped suport 76 having slots'77 through which the shaft 55 passes and transversely of which shaft said U-shaped support is movable. The I bearing 63 is fixedly mounted upon and below the table 37 but is formed with a dovetailed tenon 78 receivable within the corresponding mortise in said table whereby the fixed position of the bearing 63 with respect. .to the table may be adjustablydetermined along the table. A clamping bolt 79 carried upon the table may be turned into gripping engagement with t j bearing 63 to hold thebearing in the position to which it is adjusted. The bearing 63. also carries a guide pin 80 that passes through the base of the U-shaped support 76, this pin cooperating with the shaft'55 in positioning e tenon portion 78 of the the support 76 and -in guiding this support in movements transverse to the shaft 55. A spring 81-is interposed between the base of the U-shaped support 76 and the bearing 63, this spring serving to press the support 76 outwardly to maintain the cam rollers 74 "and 75 in engagementwith the

cams

59 and 60 respectively. The spring 81 serves to press the roller 61 toward one side of'the shaft 55 and the rollers 74 and 75 toward the other side of the shaft, the spring thus functioning to press all the rollers into engagement with the cams complemental' thereto.

place Where it is shown in engagement with the cam roller 61 to the highest portion of the cam effects such an increasing longitudinal movement of the shaft 9 to grind one end of the blade, finally causing the elevation of the point of grinding contact to grind the higher or constant portion of the cutting edge of the blade. After this portion of the. blade has been out or ground the place of grinding contact is gradually lowered to complete the grinding.

The shaft 9 is constantly turned at a uniform rate of speed, in the preferred embodiment of the invention, during all movements of the table 37. This shaft is turned by the worm gear 43 and suitable transmission mechanism which is driven by this worm gear. This transmission mechanism includes the shaft 82 upon which the worm 4L3 is fixedly mounted, the pinion 83 fixed on the shaft 82, the gear wheel 84:111 mesh with the pinion 83, the gear 85 journaled upon and beneath the table 37, this gear being elongated so that it ma remain in mesh with the gear 84 as the tab e 37 is reciprocated (the gear '84: having a fixed plane of rotation), the gear 86 fixed upon and co-axial with the gear 85, the pinion 87 also travelling with the'table 37, being rotatably mounted by means of a ball bearing structure including an inner raceway 89 fixed upon one side of the gear 88, an outer raceway- 90 fixed upon a standard 91v that is mounted upon the table 37 and the bearing balls 92 that are interposed between the raceways. The gear 88 thus rotatably mounted is fixed upon and surrounds a sleeve or enlarged hub portion 93 that carries cars 94 through which abutment screws 95 are'passed. The shaft 9 that supports the blade holder carries a collar split into halves 96, these halves being clamped together and upon the shaft by means of clamping bolts 97. Each half of the split collar carries an ear 98 interposed between a pair of abutment screws 95, there being two pairs of ears'94 on opposite sides of the shaft which carry two pairs of abutment screws on'opposite sides of the shaft in positions to recelve the ears 98 therebetween. The bore of the sleeve or hub portion 93 of the gear 88 is sufiiciently large to accommodate the largest blade holder or the largest shaft 9 supporting the same that may be a part of the grinding'machine,

temporarily or otherwise The turning'movement which is imparted to the gear 88 through the intermediation of the gears between -it and the shaft 82 is. imparted to the shaft 9 and the blade holders thereon through the intermediation of the abutment screws 95 and the split collar 96 clamped upon the shaft. To relieve the conical bearings 33 of standard 91. When the bolts 101 are loosened the jaws may be readily adjusted to have centering engagement with the shaft 9. After the adjustment has been effected tained by tightening said. bolts. its an aid in effecting the adjustment of the jaws, follower bolts 103, in threaded engagement wlth extensions 104 of the carrier 102, have abutting engagement with the outer faces of the jaws and are readily disposed so that as they are inwardly turned they may effect the inward movement of the jaws to the selected positions whereafter the bolts 101 are tightened to maintain the adjustment of the aws thus effected.

The action of the selected-cam 57 in controlling the longitudinal movement of the shaft 9 and the blade holder will now be further described in connection with Figs. 10 and 13 to 27 inclusive. The grinding wheel and blade holder rotate in opposite directions as indicated by the arrows in different figures. The substantially fixedpoint d is the point of grinding contact of the wheel, the grinding action commencing slightly below such pomtd. As the blade holder continues to turn and move longitudinally in the grind ing'operation, the point of grinding contact of the wheel at the line of the cutting edge of the blade gradually rises from a little belowv the point d until the backolf is completed an the circular are 4 (which is the constant portion of the line of the cutting edge and which cutting edge portion lies in the desired cylindrical area), is reached, the point of grinding contact remaining at this upper level until the constant portion 4: of the cutting edge has been ground whereafter the polnt of grinding contact gradually lowers to a posiit is maintion that is slightly lower than the point 03 and at which the grinding of the lead portion 5 of the cutting edge of the blade is finished.

Reference letters are employed in Figs. 12-

to 27 inclusive which diagrammatically correspond to similarly lettered parts in Fig.

10. Referring particularly to Fig. 19, the backofi portion of the cutting edge is ground,

leaving the cam roller.

roller 61Iis riding upon the portion of the cam 57 that is upon the right of the dot and dash line a and between this dot and dash line and the dot and dash line z- The actual grinding operation occurs whlle the portion of the cam 57 that is shown in Flg. 19 as being above the line z and to the right of the line zis riding upon the roller 61. The

Longitudinal movement of the shaft 9 that occurs during the grinding operation commences when the point z? of the cam 57 enters into engagement with the cam roller til-and is concluded when the point 2 0f the cam is v The return motion of the shaft 9, in the non-grinding operation, occurs between the points'z and a of the cam. When the cam roller is in engagement with the portion of the cam between the points a and e the longitudinal movement of the shaft 9 ceases preparatory to the resumption of its longitudinal movement for the grinding operation upon the ensuing blade. The dot and dash curved lines within the perimeter of the cam 57 in Fig. 1 9 are drawn to show what would be the shape of the cam if the cutting edge of the blade did not have any backoff or any lead but had-only a direction from end to end that was coincident with the constant direction of the portion 4 of the cutting edge,

so that the entire cutting edge Would, if the -cain were so modified, lie Within-a cylindrical surface. yond the dot and dash lines within the peruneter of the cam, F1 g. 19, are the cam formations which cause the recession toward the axis of such cylindrical surface of the ends of the cutting edge. The broad featuresof the invention disclosed herein are claimed in my copendingv application Serial No. 109,222 filed May 15, 1926, which is a continuation in part of the present application.

While I have herein shown and particularly described the preferred embodiment of myinv'ention I. do not wish to be limited to the "precise details of 'construction shown as changes may readily be made Without depart-o ing from the spirit of my invention, but having thus described my invention I claim as new and desire to secure by Letters Patent the following:'

1. A bladesharpening machineincluding a grinding wheel; a revolving blade,holder serving to present the blade that is to be' sharpened to said wheel; and mechanism for defining a line of grlnding contact. conforming, in part,,to an elongated blade crown and a portion receding from such crown in the plane of the blade at each end thereof, the plane of rotation of the grinding wheel Where it is in grinding contactwith the blade being substantially in a cord of the circle of rotation of the groundblade edge.

2. A blade sharpening machine including a grinding wheel; a revolving blade -holder The bulging of the cam be- I serving to hold'the blade obliquelitoithe axis of rotation of said holder; and mdehanismlfor defining a line of grinding contact that lies partially in a cylindrical area and-iii! an area tapering from said cylindricalhrea throughout each end portion of the blade? 1 3.- A blade sharpening machine including a grinding Wheel; a revolving blade holder serving to hold the blade oblique to the axis of rotation of said holder; and mechanism fort moving said holder longitudinally of its axis of rotation of said holder; and mechanism for defining a line of grinding contact that serving to hold the blade oblique to the axis lies partially in a cylindrical area and in an area tapering from said cylindrical area throughout each end portion of'the blade, thegrinding wheel being also so positioned that its blade contactingportion will pass over the blade substantially at right angles to its cutting edge. l

5. A blade sharpening machine including a grinding ,wheel; a revolving blade holder serving to hold the blade oblique to the axis of rotation of said holder; andmechanism for moving said holder longitudinally of its axis While the cutting edge of the blade is being ground in a manner to shape-said cutting edgeto lie partially in a cylindrical areaand in an area tapering from said cylindrical area throughout each end portion of the blade,- the plane of grinding contact of the grinding" wheel with the blade being substantiallyin a cord of the circle of rotation of theground blade edge, the grinding wheel being also so positioned that its blade contacting portion will pass over the blade substantially at right angles to its cutting edge.

6. A blade sharpening machine including a grindingwheel'; a revolving blade holder serving to present the blade that is to be sharpened to said wheel; and mechanism for defining a line of grinding contact conform ing, in part, to an elongated blade crown and a portionrecedingfrom such crown in the plane of the blade at each end thereof, the

' plane of rotation of the grinding wheel where it is in grindingacontact with the blade being substantially in a cord of the circle of rotation of the ground blade edge and inclinedwith respect. to .the blade holder for clearancc.

7. Ablade sharpeningmaehine including a grinding Wheel; a revolving blade holder.

serving to hold the blade oblique to the axis of rotation of said holder; and mechanism for moving said holder longitudinally of its axis while the cutting edge of the blade is being ground in a manner to shape said cutting edge to lie partially in a cylindricalarea and in an area tapering from said cylindrical area throughout each end portion of the blade, the plane of grinding contact of the grind-.

ing wheel with the blade being substantially in a cord of the circle of rotation of, the ground blade edge, the plane of rotation of the grinding wheel being inclined with, re spect to the blade holder for clearance, the grindingwheel being also so positioned that its blade contacting portion will lpass over the bladesubstantially at'right ang es to its cut-' ting edge.-

8. A blade sharpening macliinecomprising, in combination; a grinding wheel, a revolving blade holder'serving to hold a blade oblique to its axis of rotation, the axis of said grinding wheel being inclined downwardly and laterally relative to the axis of said holder, and mechanism for moving said holder longitudinally of its axis at a variable rate of speed in one direction to present said blade to the effective cutting area of said wheel in a manner to shape the cutting edge of said blade to lie partially in a cylindrical'area and partially in an area departing from said-cylindrical area. a i

- 9. A blade sharpening machine having, in combination, a grinding wheel, a continually revolving work holder serving to hold a blade oblique to its axis of rotation, said grinding 7 wheel being inclined downwardly and laterally relative to the axis of said holder to present a portion thereof as its effective grinding area, and means for reciprocating said holder longitudinally of its axis to present said blade to said grinding wheel in a manner such that the point of engagement thereof with said grinding wheel shifts slightly at each end of.

-while the cutting edge of said blade is being ground in a manner to shape the same to lie partially in a cylindrical area and partially in area tapering from said cylindrical area.

11.. A blade sharpening machine having, in combination, a grinding wheel, a revolving holder serving to oblique to the axis of rotation of said holder,

hold a plurality ofblades" said grinding wheel being inclined laterally to present one edge as its effective grinding area, and inclined downwardly to avoid interference with the blades adjacent the one being ground, and means for reciprocating I said holder longitudinally to present said blades successively to the effective grinding area of said wheel, the reciprocation during each cutting stroke being variable to shift the point of grinding contact at certain points along the cutting edge of each blade.

12. A blade sharpening machine having, in

combination, a grinding wheel, a revolving blade holder serving to hold a plurality of spaced blades oblique to the axis of rotation of said holder, said grinding wheel spindle being inclined laterally to provide clearance in grinding each blade and downwardly to avoid interference with adjacent blades, and means'for reciprocating said holder axially in timed relation to the rotation thereof to automatically present successive blades to said wheel, the speed of reciprocationbeing'slightly varied during each grinding stroke to grind an offset portion on eachblade.

13. A blade sharpening machine comprising, in combination, a cup-shaped grinding wheel, a blade holder serving to hold a blade oblique to its axis of rotation, the plane of rotation of said grinding wheel being inclined with respect to said blade holder, means for effecting a relative reciprocatory movement axially of said holder between said grinding wheel and said holder, and means connected to said first mentioned means for rotating said holder in predetermined relation to said reciprocation, said means serving to vary said relationship at predetermined points in the cutting stroke to shift the point of engagement of said blade with said grinding wheel.

14. A blade sharpening machine comprising, in combination, an annular grinding wheel, a blade holder serving to hold a blade oblique to its axis of rotation, said grinding wheel being positioned with a diameter in line with said blade" and being inclined about said diameter, and mechanism for revolving said holder and for effecting a relative reciprocation between said grinding wheel and said holder axially of said holder, said mechanism being operable to vary the rate of said reciprocation in one direction during the cutting stroke to present said blade to different points on said grinding wheel in a manner to, obtain a predetermined contour.

15. In a grinding machine, in combination,

a grinding wheel, a blade holder havingoafl blade inclined to its axis, means for rotating said blade holder, and means for reciprocating said blade holder across said grinding wheel, said'last mentioned means including a table for supporting said blade holder, a plurality of cams of different shapes and cam I mums follower means adjustable on said table for 7 selective cooperative engagement with said cams;

16. Ina grinding machine, in combination,

a a grinding wheel, a work holder, a table,

stocks on said table for supporting the vwork holder arbor, mechanism for reciprocating said table, and mechanism connected to said first mentioned mecha nism for rotating said arbor, said last mentioned mechanism com 10 prising a gear housing through which the arbor extends, gear means connected to said arbor, and means for centering said arbor in termediate its ends.

In Witness whereof, I hereunto subscribe 15